adc
ADC hardware, built-in PIC ADC module
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Author
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Stef Mientki, Copyright © 2002..2008, all rights reserved.
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Adapted-by
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Sebastien Lelong, Rob Hamerling.
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Compiler
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2.4o
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Description
Library to handle ADC peripheral, supporting:
- low (8-bits) and high (16-bits) resolution (whatever the PIC supports)
- ADC pin configuration
- channel selection
- clock selection
- reference voltage selection
Q: How to use it?
A: See http://justanotherlanguage.org/content/jallib/tutorials/tutorial_adc_intro
About Vref setup:
- when ADC_NVREF = ADC_NO_VREF : there's no Vref pin used, vref is done
internally, using power supply (Vdd <-> Vss)
- when ADC_NVREF = ADC_VREF_POS: there's only one Vref pin, this is Vref+
- when ADC_NVREF = ADC_VREF_POS_NEG: two Vref pins are used, Vref+ and Vref-
- when ADC_NVREF = ADC_VREF_NEG: there's only one Vref pin, this is Vref-
- when ADC_NVREF = ADC_VREF_FVR: Vref pin internally connected to FVR module if present
(user should setup FVRCON as desired).
A major trigger is when using ADC libs is ADC_DYNAMIC.
When declared, several parameters become dynamic and can be changed
at runtime. This includes:
- ADC_NCHANNEL: the number of used ADC channels (dependent channels only,
independent channels are always selected at runtime with set_analog_pin() ).
- ADC_TEMP Careful, computation related to temperature very approximative
- ADC_RSOURCE
Notes
This is a heavy refactoring/rewriting of original library of Stef Mientki.
adc_channels.jal and adc_clock.jal.
The original library can be found:
- Stef's: http://mientki.ruhosting.nl/pic-tools/jal/libs2/adc_hardware.jal
- Jallib issue tracker: http://code.google.com/p/jallib/issues/detail?id=7
The main changes are about ADC configuration, which are essentially handled in
adc_channels.jal and adc_clock.jal.
Dependencies
Private
Private
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adc_init()
Tilte: Initialise ADC module and default parameters
Arguments: (none)
Returns: nothing
Initializes the PIC AD-converter,
by calling the correct routine according to the number of external references
Settings are done according to the special ADC constants
Sets analog pins to input
Calculate aquisition time
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adc_read_bytes(byte in adc_chan, byte out adc_hbyte, byte out adc_lbyte)
Title: Deprecated procedure, replaced by function adc_read_high_res()
Private
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adc_read_high_res(byte in adc_chan) return word
Title: Analog to digital conversion returning a 16-bits value
Arguments: channel number
Returns: 16-bits ADC value
Notes: - Uses right justification
Returns a 16-bits value of the result of ADC, of which the
range is dependent of the supported ADC resolution of the PIC
(can be a 8-, 10-, 12-bits value).
When the PIC supports only 8-bits ADC resolution the
result is the same as of adc_read_low_res().
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adc_read(byte in adc_chan) return word
Title: Deprecated function, replaced by adc_read_high_res()
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adc_read_low_res(byte in adc_chan) return byte
Title: Analog to digital conversion returning an 8-bits value
Arguments: Channel number
Returns: 8-bits ADC value
Notes: - Uses left justification.
Returns the 8 most significant bits of the result of ADC
Private
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_adc_read(byte in adc_chan, bit in justify) return word
Title: Analog to Digital conversion of the selected channel.
Arguments: - channel number (byte)
justification (bit 0=left, 1=right)
Returns: word with ADC value
Notes: - When PIC supports high resolution (more than 8 bits)
all bits of the ADC conversion are stored straight over
from ADRESH and ADRESL. When PIC supports only 8-bits
resolution only the contents of ADRES are stored.
With right justification the result is immediately
usable as binary value.
Left justification allows easy selection of the 8 most
significant bits of the result, regardless which
resolution the PIC supports (can be 8-,10 or 12-bits).
Here are the list of samples which use this library: